The present invention generally pertains to the hobby-mechanical industry. More specifically, the present invention pertains to means for extending the torque and/or rotational capacity of a hobby servo.
A servo motor (a.k.a. simply a “servo”) is a device having a rotatable output shaft. The output shaft can typically be positioned to specific angular positions in accordance with a coded signal received by the servo. It is common that a particular angular position will be maintained as long as a corresponding coded signal exists on an input line. If the coded signal changes, the angular position of the shaft will change accordingly. Control circuits and a potentiometer are typically included within the servo motor casing and are functionally connected to the output shaft. Through the potentiometer (e.g., a variable resistor), the control circuitry is able to monitor the angle of the output shaft. If the shaft is at the correct angle, the motor actuates no further changes. If the shaft is not at the correct angle, the motor is actuated in an appropriate direction until the angle is correct.
There are different types of servo motors that include output shafts having varying rotational and torque capabilities. For example, the rotational and/or torque capability of an industrial servo is typically less restricted than that of a hobby servo. That being said, hobby servos are generally available commercially at a cost that is much less than that associated with industrial servos.
Because hobby servos are relatively small and inexpensive, they are popular within the hobby-mechanical industry for applications such as, but by no means limited to, hobby robotic applications and radio-controlled models (cars, planes, boats, etc.). One example of a hobby servo is the Futaba S-148 available from Futaba Corporation of America located in Schaumburg, Ill.
The output shaft of a hobby servo is typically capable of traveling approximately 180° (possibly up to 210° or more depending on manufacturer). Rotation of the hobby servo shaft is limited typically by one or more internal mechanical stops. It is also typically true that the output shaft of a hobby servo is capable of producing a relatively limited amount of torque power. The torque and rotational limitations of a hobby servo are adequate for many hobby applications, such as model car steering control, puppet control, robot arm or head movement and/or model airplane rudder control. It is true, however, that some applications require a servo having torque power and/or a rotational capacity that is beyond the capability of a typical hobby servo. Increased torque power and/or rotational capacity enable greater mechanical flexibility.
Some hobby servos can be mechanically altered to provide an extended range of rotation. However, this solution requires mechanical alteration that often only works for some types of servos. Rotational control for most hobby servos is limited by the internal potentiometer being utilized to monitor rotation. When a hobby servo is hacked to extend the rotational capacity, the internal potentiometer of the servo will, in most instances, not be configured to monitor angular positions too far beyond the original range of rotation. The control system of a hacked servo will commonly not be configured to accurately position the servo output shaft too far within the extended range of rotation. For this reason, it becomes difficult to control rotation once a hobby servo has been adapted for extended rotation.